Mail PTR Records

[John Hinton]

Phil Udel wrote:
>
> I have been thinking that I might try to reject mail that does not 
> have a Ptr.
>
> Example:
>
> “Non-existent CNAMEReports CNAME of 178.128/25.240.39.12.in-addr.arpa.
> 12.39.240.178 has no reverse DNS entry; some mail servers may not 
> accept your mail”
>
> If I stop it at the sendmail.mc with a FEATURE(`require_rdns')dnl then 
> I will not have any way to track what I might need to allow.
>
> If I use the SA RDNS_NONE and RDNS_DYNAMIC then I waste CPU but get 
> nice reporting.
>
> What would you guys suggest, any other pitfalls?
>
I do this at the sendmail level. It does show in my logs. Almost all of 
the big ISPs block at this level, so if anyone does not have PTR setup, 
they are unable to mail to a huge portion of the internet... I would not 
personally allow it past sendmail due to the extra loads. I always try 
to reject as early as possible on the most obvious items. Bad recipient, 
no rev dns and spamhaus.

John Hinton